A detailed investigation on UV/H2O2 photooxidation has been carried out in order to determine the kinetics of the oxidative degradation of phenol and 2- and 4-chlorophenols in dilute aqueous solutions. Effects of different process parameters, such as initial substrate and H2O2 concentrations, substrate to H2O2 ratio on the degradation kinetics of the phenolic substrates, have been studied. Degradation rates of phenol and chlorophenols are insignificantly small with ultraviolet radiation only and also with hydrogen peroxide (in the absence of UV radiation), but the synergistic effect of UV/H2O2 results in a marked enhancement of the rates of degradation. A mechanistic model for UV/H2O2 photooxidation has been developed. Room temperature (27°C) rate constants for the reaction of (·)OH radical (formed by absorption of photons) with the substrates have been estimated by using the model equation. The calculated rate constants are of the same order of magnitude as reported for other similar aromatic compounds. Copyright (C) 1999 Elsevier Science B.V.

ASIM DE

Chemical Engineering

B CHAUDHURI

S BHATTACHARJEE

B K DUTTA

University of Calcutta (informally known as Calcutta University or CU) is a collegiate public state university located in Kolkata, West Bengal, India.&nbsp;Within India it is recognized as a &quot;Five-Star University&quot; and accredited &quot;A&quot; Grade by National Assessment and Accreditation Council.

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The University of Calcutta has secured the Fifth position among the Universities of India in the prestigious &quot;Indian University Ranking 2019&quot; list, released by the NIRF of the Ministry of Human Resource Development, Government of India.

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It was established on 24 January 1857, and was one of the first institutions in Asia to be established as a multidisciplinary and Western-style university. Its alumni and faculty include several heads of state, heads of government, social reformers, prominent artists, only academy award winner and Dirac medal winner in India, many Fellows of the Royal Society and five Nobel laureates as of 2019 which is highest in South Asia.

University Of Calcutta

Estimation of .OH radical reaction rate constants for phenol and chlorinated phenols using UV/H2O2 photo-oxidation.

Journal of Hazardous Materials

Disposal of waste plastics imposes serious problems to the environmentalists, since plastics are non-biodegradable and emit carcinogenic gases when incinerated. In a country like India, where solar energy is abundantly available, semiconductor photo catalysis may be a clean and economic technology to combat such a problem. In the present work we addressed to the problem of degrading polyvinyl chloride (PVC) by photo catalysis by exposing a PVC-ZnO composite film to solar radiation as well as to artificial UV radiation in presence of water and air. Degradation in the two processes has been compared. The surface morphology as well as the FTIR spectroscopy of the irradiated film has been critically examined. The degradation was measured by weight loss data and was found to follow a pseudo-first order rate equation. The various parameters studied were loading of the semiconductor and intensity of UV radiation. A possible mechanism has been suggested and the corresponding rate equation has been modeled. The model has been validated by the experimental data. © 2010 Elsevier Ltd. All rights reserved.

Solar Energy

Photocatalytic degradation of PVC-ZnO composite film under tropical sunlight and artificial UV radiation: A comparative study

White or plastic pollution has become a serious concern to the environmentalists for the last few years. Degradation of waste plastics in conventional incinerators leads to emission of carcinogenic dioxins to the atmosphere. In this work, an attempt has been made for the photocatalytic degradation of polyvinyl chloride (PVC) using ZnO as semi-conductor catalyst in the form of PVC-ZnO composite film. The surface morphology as well as the FTIR spectroscopy of the irradiated film has been critically examined. The degradation was measured by weight loss data and was found to follow a pseudo-first order rate equation. The various parameters studied were loading of the semi-conductor, intensity of UV radiation and presence of Eosin Y as a sensitizing dye. It was observed that dye-sensitization enhanced degradation of PVC to a large extent. A possible mechanism has been suggested and the corresponding rate equation has been modeled for the dye-sensitized rate of degradation. The model has been validated by the experimental data. © 2007 Elsevier B.V. All rights reserved.

Degradation mechanism and kinetic model for photocatalytic oxidation of PVC-ZnO composite film in presence of a sensitizing dye and UV radiation

Fenton-generated hydroxyl radicals removes the color of the malachite green, a basic dye with triphenylmethane group, almost (∼98%) completely in wcakly acidic aqueous media possibly through oxidative degradation pathways as evidenced from a remarkable lowering in the COD value of the product mixture in comparison to the title dye under identical conditions and almost full quenching of the reaction in presence of hydroxyl radical scavengers. The dye can most effectively be degraded at dye:Fe2+:H2O2 molar ratio of 1:3.3:81.7 for 1.08 × 10-5 mol dm-3 dye at pH 2.5-2.8 and at 299K. The rate law of the dye degradation process appears to be: -d[dye]/dt=k[dye] [Fe2+]0.79 [H2O2]0.12, where k=(33±5) (dm3 mol-1)0.91 s-1 at 299K. Salts like NaCl or NaBr retard the degradation rate markedly whereas SO42- or ClO4- are rather innocent. In presence of Cl-, the radical reaction: ClOH·- + Fe2+→Cl-+HO-+Fe3+ may account for the gross lowering of degradation rate. The results may be helpful for designing the treatment plants of wastewater containing dyes with triphenylmethane group.

Journal of Environmental Science and Health - Part A Toxic/Hazardous Substances and Environmental Engineering

Oxidative degradation of malachite green by Fenton generated hydroxyl radicals in aqueous acidic media

A detailed investigation on the kinetics of the oxidative degradation of a reactive dye, C. I. Reactive Red 2 by hydroxyl radicals generated by H2O2 and Fe2+ has been carried out in aqueous acidic media. Effects of different parameters like initial concentration of dye, H2O2, Fe2+, pH of the solution, reaction temperature and added electrolytes on the oxidation process have been studied. The results indicate that 1.63 x 10-4 mol dm-3 dye can be most effectively degraded at a dye: Fe2+: H2O2 molar ratio of 1:0.22:8.13 at pH ∼ 2.7 and at 299 K. The addition of excess 2-propanol or t-butyl alcohol, well known scavengers of hydroxyl radicals, almost stopped the degradation of the dye indicating the absence of any possible reductive pathways in the degradation. The results may be useful for designing the treatment systems of wastewater containing various reactive dyes.

Journal of Environmental Monitoring

Chemical oxidation of C. I. Reactive red 2 using fenton-like reactions

Oxidative degradation of phenol by H2O2 and ultraviolet radiation is carried out, and a kinetic model is derived in order to represent the photooxidation reaction. The model equations are fitted by the experimental data collected for two distinct phases of reaction, marked as phase I and phase II. In the first phase H2O2 concentration is the controlling factor in the degradation process, whereas in the second phase concentration of phenol is the controlling species. A mechanistic explanation of the behavior has been presented.

Journal	Journal of Hazardous Materials
Publisher	-
ISSN	0304-3894
Open Access	No